The present invention relates to a master cylinder which is advantageously used in, for example, a brake or a clutch for a vehicle.
Generally, a master cylinder used in a vehicle, such as an automobile, mainly comprises a cylinder body having a boss on an outer circumferential surface thereof, a reservoir having on its bottom a supply fitting to be connected to the boss of the cylinder body and a grommet seal having a cylindrical portion and a flange portion. The cylindrical portion of the grommet seal serves to seal a space between an inner circumferential surface of the boss of the cylinder body and an outer circumferential surface of the supply fitting of the reservoir.
With respect to the above-mentioned master cylinder, for example, Unexamined Japanese Utility Model Public Disclosure No. 55-161747 discloses a master cylinder including a grommet seal which serves as a connecting member for connecting the cylinder body and the reservoir by engagement.
In the master cylinder disclosed in Unexamined Japanese Utility Model Public Disclosure No 55-161747, the boss of the cylinder body has a first engaging projection which Projects Radially inwards from the boss on a side of an open end thereof. The supply fitting of the reservoir has a second engaging projection which projects radially outward from an outer circumferential surface of the supply fitting.
In this master cylinder, the cylinder body and the reservoir are connected as stated below. That is, the grommet seal is fitted into the boss of the cylinder body to thereby engage the first engaging projection with an outer circumferential surface of the grommet seal. The supply fitting of the reservoir is pushed into the grommet seal fitted in the boss to thereby engage the second engaging projection with an inner circumferential surface of the grommet seal. Thus, the grommet seal engages both the first engaging projection formed in the boss of the cylinder body and the second engaging projection formed in the supply fitting of the reservoir; Consequently the cylinder body and the reservoir are connected while being engaged with the grommet seal provided therebetween.
In the above-mentioned conventional master cylinder, although means for connecting the cylinder body and the reservoir is provided, the grommet seal also serves as a connecting member for connecting the cylinder body and the reservoir. In order to firmly connect the cylinder body and the reservoir by engagement, the grommet seal is arranged to be capable of being fitted between the boss and the supply fitting without any clearance. That is, the grommet seal has a dimension which causes a high degree of interference when the supply fitting is inserted into the grommet seal fitted in the boss.
When the supply fitting is inserted into the grommet seal which has been fitted into the boss, resistance to insertion is high due to the high degree of interference from the grommet seal. Therefore, to connect the boss of the cylinder body and the supply fitting of the reservoir, a machine, such as a press-fitting machine, must be used. Thus, an operation for assembling a master cylinder requires the use of equipment and is cumbersome, thereby lowering productivity.
Further, when the supply fitting is forcibly press-fitted into the grommet seal using the press-fitting machine, the grommet seal suffers abnormal deformation because portion thereof is driven into an interface between the grommet seal and an associated surface and is therefore likely to be damaged. When the grommet seal is damaged, leakage of hydraulic fluid occurs, thereby lowering reliability of the grommet seal.